NanoSatC-Br1 is the first CubeSat project of Brazil, developed at the Southern Regional Space Research Center (CRS/CCR/INPE-MCT) in collaboration with the Space Science Laboratory of the Federal University of Santa Maria (LACESM/CT - UFSM), Santa Maria, RS, Brazil. The INPE (Instituto de Pesquisas Espaciais) South Regional Center is in fact located on the campus of UFSM (Federal University of Santa Maria) and collaboration between the two institutions is of importance for mission success. The mission has three objectives in the fields of science, technology validation, and academic i.e., student involvement in all mission phases. 1)2)3)4)5)

The CubeSat project is considered to be a capacity building mission with the goal to involve a new generation of scientists and engineering students through a CubeSat program, providing hands-on training and learning dealing with aerospace technologies and space weather issues. The NanoSatC-BR project made it possible to involve Brazilian universities, such as UFSM (Federal University of Santa Maria), in the Brazilian Space Program with a collaboration of INPE. CRS acts as the NanoSatC-BR1 mission general manager and PI in collaboration with INPE.

The objective of the mission is to provide monitoring of Earth's magnetosphere by measuring the magnetic field over Brazil and to study the magnetic phenomena of the SAA (South Atlantic Anomaly) and the EEJ (Equatorial Electrojet). Note: This SAA is also referred to as SAMA (South Atlantic Magnetic Anomaly).

• One feature of particular interest is the South Atlantic Anomaly (SAA), an area where the radiation hazard from high proton fluxes and cosmic rays is high due to the relatively low shielding effect provided by the Earth's magnetic field. In this area, for example, a significantly higher number of so-called SEUs (Single Event Upsets) occur in LEO (Low Earth Orbiting) satellites (Heirtzler, 2002, Figure 1).

• The EEJ (Equatorial Electrojet) is a narrow ribbon of current flowing eastward in the day time equatorial region of the Earth's ionosphere. The abnormally large amplitude of variations in the horizontal components measured at equatorial geomagnetic observatories, as a result of EEJ, was noticed as early as 1920 from ground observations. The EEJ phenomenon was first identified using geomagnetic data. The amplitude of the daily variation of the horizontal magnetic intensity (ΔH) measured at a geomagnetic observatory near the dip-equator is 3–5 fold higher than the variation of data from other regions of Earth. A typical diurnal equatorial observatory data show a peak of strength ~80 nT at 12:00 hours LT (Local Time), with respect to the night-time level.

EEJ studies from satellite data were initiated with the arrival of data from the POGO (Polar Orbiting Geophysical Observatories) series of satellite (1967–1970). The characteristic signature of the EEJ is a sharp negative V-shaped curve in the ΔH field, attaining its minimum within 0.5º of the magnetic dip equator. The magnetic data from satellite missions like Ørsted (1999–present) and CHAMP (2000–2010) have vastly improved our knowledge of the EEJ (Figure 2). 6)

The NanoSatC-BR1 concept was developed to:

• monitor, in real-time the geospace, the particle precipitation and the disturbances at the Earth's magnetosphere over the Brazilian territory

• determine their effects on regions such as the South Atlantic Magnetic Anomaly (SAMA).

NanoSat-BR1 is a 1U CubeSat of size of 10 cm x 10 cm x 11.3 cm and a mass of ~ 1 kg. A 1U CubeSat kit of ISIS (Innovative Solutions In Space BV, Delft, The Netherlands) was purchased while the local work has been concentrated in the development of the payload and in the students participation in activities such as mission analysis and design, integration, testing and operation, besides specific studies on the platform itself. 8)

The satellite uses the standard CubeSat features , body-mounted solar panels, Li-ion batteries, a basic attitude determination and control system and processor cards to control all spacecraft functions.

RF communications: Use of an amateur UHF/VHF band radio transceiver for downlink and uplink communications. In addition, an S-band link is used. The S-band stations are located in São José dos Campos at ITA (Instituto Tecnológico de Aeronáutica), and at INPE South Regional Center in the southern part of Brazil.

Figure 5: Proposed operational test set up suggested by the vendor of the platform (image credit: ISIS)

Legend to Figure 5: Since INPE has a very large AIT (Assembly, Integration and Test) facility, called LIT, it is not clear yet which facility will be used for the system operational testing.

Launch: The NanoSatC-Br1 CubeSat was launched as a secondary payload on June 19, 2014 (19:11:11 UTC) on a Dnepr-1 vehicle of ISC Kosmotras (cluster launch). The launch site was the Yasny Cosmodrome in the Dombarovsky region of Russia. 9)10)11)

The primary payloads on this flight were the Deimos-2 minisatellite (310 kg) of Deimos Elecnor, Spain, and the KazEOSat-2 minisatellite (185 kg) of Kazcosmos, Kazakhstan.

• UNISat-6, a microsatellite of GAUSS at the University of Rome (La Sapienza), Italy. UniSat-6 (26 kg) includes Pico-Orbital Deployers and PEPPODs (Planted Elementary Platform for Picosatellite Orbital Deployment) systems for the release of four CubeSats from the spacecraft. These four satellites are:

• Perseus-M1 and M2, two identical 6U CubeSats of Canopus Systems US / Dauria Aerospace. The nanosatellites are carrying an AIS payload for ship tracking.

• QB50P1 and QB50P2, two 2U CubeSats (2 kg each) of Von Karman Institute, Brussels, Belgium. These are two precursor satellites to the QB50 project that will launch a network of 50 satellites by a team of 15 universities and institutions around the world.

• NanoSatC-Br1, a 1U CubeSat of the Southern Regional Space Research Center and of INPE, Brazil

• DTUSat-2, a 1U CubeSat of DTU (Technical University of Denmark), Lyngby, Denmark

• July 19, 2015: Today, NanoSatC-Br1 is 1 year on orbit. Since the battery is no longer managing to retain its charge, only transmissions in the sunlit phase of the orbit are possible to monitor the health of the spacecraft and its subsystems. The CubeSat operates nominally when the battery charge exceeds the minimum limit of 6.5 V. Due to this situation, the project is very much dependent on information provided by the amateur radio community. 13)

• November 19, 2014: NanoSatC-Br1 completed 5 months on orbit. Despite the operational difficulties caused by the low battery voltage in the last 30 days, the CubeSat has generated about 4 months of data in nominal operation, obtained in more than 1,500 orbits. 14)

- The magnetometer data from NanoSatC-Br1 confirm the presence of the South Atlantic Magnetic Anomaly (SAMA). The values of the magnetic field strength are consistent with those obtained by the models of the International Association of Geomagnetism and Aeronomy (IAGA). "With NanoSatC-Br1 we confirm the forecast of the expected values of the intensity of the Total Magnetic Field of the Earth, as predicted by the IGRF (International Geomagnetic Reference Field) model of IAGA and the IUGG (International Union of Geodesy and Geophysics)," said Nelson George Schuch, CRS (Southern Regional Center) researcher of INPE, located in Santa Maria (RS), and the NANOSATC-BR program coordinator. "These are the first data generated by a Brazilian scientific satellite," commented Otavio Durão of INPE, who coordinates the project activities in São José dos Campos (SP). 15)

- A pre-scientific analysis of the observations collected by the XEN-1210 magnetometer in operation aboard the NanoSatC-Br1, shows an excellent correlation of data compared to theoretical figures for the intensity of the geomagnetic field at the same altitude with the theoretical IGRF model of IAGA / IUGG. The data analysis is coordinated by Marlos Rockenbach da Silva, of CRS / INPE.

- The Figure 6 shows a map of the total Geomagnetic field intensity for an altitude of 614 km for the South America, a region domain Magnetic Anomaly South America (AMAS), showing that the spatial variation of the total intensity of the field varies between 24.000 nT at the edge and 17,000 nT at the center in the AMAS.

Figure 6: Map of the total intensity of the Geomagnetic Field to altitude of 614km over South America, domain region of AMAS, where the red line indicates the approximate orbit of NanoSatC-Br1 on August 17, 2014, from 10: 57h to 11: 07h; the right side of the line presents the Geomagnetic field intensity values observed and collected by NanoSatC-Br1 in that orbit (image credit: INPE, UFSM)

• On October 17, 2014, NanoSatC-Br1 reported low battery voltage problems. Consequently, the transmission of payload data is affected, which functioned nominally for the last 3 months. 16)

• July 19, 2014: INPE is reporting having good contact with their NanoSatC-Br1 CubeSat, providing nominal operations. During the first month on orbit, data from NanoSatC-Br1 were received at the stations of Santa Maria, São José dos Campos and amateur radio in Brazil and abroad. 17)

Sensor complement: (FGM, ICs)

FGM (Fluxgate Magnetometer):

The science instrument is a XEN-1210 FGM (Fluxgate Magnetometer) from Xensor Integration BV, Delft, The Netherlands. The objective is to measure the intensity of Earth's magnetic field in the SAA (South Atlantic Anomaly) region and the EEJ (Equatorial Electrojet). 18)

A second magnetometer (XEN-1210) is used for attitude determination by the satellite attitude determination and control subsystem. The magnetometers chosen fit with the technical and scientific aspects of the satellite proposal.

The requirements for the magnetometer are listed below:

• Collect data in a frequency at least three frames per second

• Get information about the three components of the geomagnetic field

• The data must be available at least once daily

• The acceptable intensity resolution of the magnetic field must be 15nT.

The XEN-1210 FGM is a magnetic field sensor based on the Hall effect. It uses Xensor's patented high performance Hall technology, with a resolution of 15nT and a magnetic field range of 63mT. The device is available in the SFN8 package (Figure 7). 19)

Figure 7: Various illustrations of the XEN-1210 FGM along with a 3D board of 3 XEN-1210 sensors mounted in 3 orientations (image credit: Xensor Integration)

In addition to the science payload, two technological payloads are flown using different implementation techniques; the objectives are to test their radiation resistance in space. These are the first circuits designed in the country for space applications that will fly on a spacecraft (Ref. 5).

1) An industrial FPGA for which the Brazilian university,UFRGS (Universidade Federal do Rio Grande do Sul) developed a fault tolerant software in VHDL, in order to operate it in a radiation intense environment. A fault tolerant software was developed in order to provide radiation protection to a standard commercial FPGA.

Besides testing the FPGA behavior under radiation in space, this group is also developing the board where the three payloads will be placed (magnetometer, on/off driver and FPGA).

2) A driver IC designed by a Brazilian software house located on the campus of UFSM (Federal University of Santa Maria), also to be tested for radiation resistance.

Driver on/off IC: This circuit was designed by the Santa Maria Design House, located at UFSM using a library also developed in house for radiation hardening characteristics. The requirements were stated by INPE's Aerospace Electronic Division for a possible support of its future missions. The functional capability of the driver on/off IC is to receive on/off telecommands from the satellite bus and direct them to the various payload equipment destinations.

The prototype of the circuit was manufactured and is available (digital part) incorporating other functions of interest as well such as a transition set and shift registers to measure radiation dosages.

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).